// //////////////////////////////////////////////////////////
// sha256.cpp
// Copyright (c) 2014,2015 Stephan Brumme. All rights reserved.
// see http://create.stephan-brumme.com/disclaimer.html
//

#include "sha256.h"

// big endian architectures need #define __BYTE_ORDER __BIG_ENDIAN
#if !defined(_MSC_VER) && defined(__APPLE__)
#include <machine/endian.h>
#elif !defined(_MSC_VER)
#include <endian.h>
#endif

/// same as reset()
SHA256::SHA256()
{
	reset();
}

/// restart
void SHA256::reset()
{
	m_numBytes = 0;
	m_bufferSize = 0;

	// according to RFC 1321
	m_hash[0] = 0x6a09e667;
	m_hash[1] = 0xbb67ae85;
	m_hash[2] = 0x3c6ef372;
	m_hash[3] = 0xa54ff53a;
	m_hash[4] = 0x510e527f;
	m_hash[5] = 0x9b05688c;
	m_hash[6] = 0x1f83d9ab;
	m_hash[7] = 0x5be0cd19;
}

namespace {
inline uint32_t rotate(uint32_t a, uint32_t c)
{
	return (a >> c) | (a << (32 - c));
}

inline uint32_t swap(uint32_t x)
{
#if defined(__GNUC__) || defined(__clang__)
	return __builtin_bswap32(x);
#endif
#ifdef MSC_VER
	return _byteswap_ulong(x);
#endif

	return (x >> 24) | ((x >> 8) & 0x0000FF00) | ((x << 8) & 0x00FF0000) | (x << 24);
}

// mix functions for processBlock()
inline uint32_t f1(uint32_t e, uint32_t f, uint32_t g)
{
	uint32_t term1 = rotate(e, 6) ^ rotate(e, 11) ^ rotate(e, 25);
	uint32_t term2 = (e & f) ^ (~e & g); //(g ^ (e & (f ^ g)))
	return term1 + term2;
}

inline uint32_t f2(uint32_t a, uint32_t b, uint32_t c)
{
	uint32_t term1 = rotate(a, 2) ^ rotate(a, 13) ^ rotate(a, 22);
	uint32_t term2 = ((a | b) & c) | (a & b); //(a & (b ^ c)) ^ (b & c);
	return term1 + term2;
}
} // namespace

/// process 64 bytes
void SHA256::processBlock(const void *data)
{
	// get last hash
	uint32_t a = m_hash[0];
	uint32_t b = m_hash[1];
	uint32_t c = m_hash[2];
	uint32_t d = m_hash[3];
	uint32_t e = m_hash[4];
	uint32_t f = m_hash[5];
	uint32_t g = m_hash[6];
	uint32_t h = m_hash[7];

	// data represented as 16x 32-bit words
	const uint32_t *input = (uint32_t *)data;
	// convert to big endian
	uint32_t words[64];
	int i;
	for (i = 0; i < 16; i++)
#if defined(__BYTE_ORDER) && (__BYTE_ORDER != 0) && (__BYTE_ORDER == __BIG_ENDIAN)
		words[i] = input[i];
#else
		words[i] = swap(input[i]);
#endif

	uint32_t x, y; // temporaries

	// first round
	x = h + f1(e, f, g) + 0x428a2f98 + words[0];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0x71374491 + words[1];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0xb5c0fbcf + words[2];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0xe9b5dba5 + words[3];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0x3956c25b + words[4];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0x59f111f1 + words[5];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0x923f82a4 + words[6];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0xab1c5ed5 + words[7];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// secound round
	x = h + f1(e, f, g) + 0xd807aa98 + words[8];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0x12835b01 + words[9];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0x243185be + words[10];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0x550c7dc3 + words[11];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0x72be5d74 + words[12];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0x80deb1fe + words[13];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0x9bdc06a7 + words[14];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0xc19bf174 + words[15];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// extend to 24 words
	for (; i < 24; i++)
		words[i] = words[i - 16] +
			   (rotate(words[i - 15], 7) ^ rotate(words[i - 15], 18) ^
			    (words[i - 15] >> 3)) +
			   words[i - 7] +
			   (rotate(words[i - 2], 17) ^ rotate(words[i - 2], 19) ^
			    (words[i - 2] >> 10));

	// third round
	x = h + f1(e, f, g) + 0xe49b69c1 + words[16];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0xefbe4786 + words[17];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0x0fc19dc6 + words[18];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0x240ca1cc + words[19];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0x2de92c6f + words[20];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0x4a7484aa + words[21];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0x5cb0a9dc + words[22];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0x76f988da + words[23];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// extend to 32 words
	for (; i < 32; i++)
		words[i] = words[i - 16] +
			   (rotate(words[i - 15], 7) ^ rotate(words[i - 15], 18) ^
			    (words[i - 15] >> 3)) +
			   words[i - 7] +
			   (rotate(words[i - 2], 17) ^ rotate(words[i - 2], 19) ^
			    (words[i - 2] >> 10));

	// fourth round
	x = h + f1(e, f, g) + 0x983e5152 + words[24];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0xa831c66d + words[25];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0xb00327c8 + words[26];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0xbf597fc7 + words[27];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0xc6e00bf3 + words[28];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0xd5a79147 + words[29];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0x06ca6351 + words[30];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0x14292967 + words[31];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// extend to 40 words
	for (; i < 40; i++)
		words[i] = words[i - 16] +
			   (rotate(words[i - 15], 7) ^ rotate(words[i - 15], 18) ^
			    (words[i - 15] >> 3)) +
			   words[i - 7] +
			   (rotate(words[i - 2], 17) ^ rotate(words[i - 2], 19) ^
			    (words[i - 2] >> 10));

	// fifth round
	x = h + f1(e, f, g) + 0x27b70a85 + words[32];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0x2e1b2138 + words[33];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0x4d2c6dfc + words[34];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0x53380d13 + words[35];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0x650a7354 + words[36];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0x766a0abb + words[37];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0x81c2c92e + words[38];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0x92722c85 + words[39];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// extend to 48 words
	for (; i < 48; i++)
		words[i] = words[i - 16] +
			   (rotate(words[i - 15], 7) ^ rotate(words[i - 15], 18) ^
			    (words[i - 15] >> 3)) +
			   words[i - 7] +
			   (rotate(words[i - 2], 17) ^ rotate(words[i - 2], 19) ^
			    (words[i - 2] >> 10));

	// sixth round
	x = h + f1(e, f, g) + 0xa2bfe8a1 + words[40];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0xa81a664b + words[41];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0xc24b8b70 + words[42];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0xc76c51a3 + words[43];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0xd192e819 + words[44];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0xd6990624 + words[45];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0xf40e3585 + words[46];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0x106aa070 + words[47];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// extend to 56 words
	for (; i < 56; i++)
		words[i] = words[i - 16] +
			   (rotate(words[i - 15], 7) ^ rotate(words[i - 15], 18) ^
			    (words[i - 15] >> 3)) +
			   words[i - 7] +
			   (rotate(words[i - 2], 17) ^ rotate(words[i - 2], 19) ^
			    (words[i - 2] >> 10));

	// seventh round
	x = h + f1(e, f, g) + 0x19a4c116 + words[48];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0x1e376c08 + words[49];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0x2748774c + words[50];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0x34b0bcb5 + words[51];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0x391c0cb3 + words[52];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0x4ed8aa4a + words[53];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0x5b9cca4f + words[54];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0x682e6ff3 + words[55];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// extend to 64 words
	for (; i < 64; i++)
		words[i] = words[i - 16] +
			   (rotate(words[i - 15], 7) ^ rotate(words[i - 15], 18) ^
			    (words[i - 15] >> 3)) +
			   words[i - 7] +
			   (rotate(words[i - 2], 17) ^ rotate(words[i - 2], 19) ^
			    (words[i - 2] >> 10));

	// eigth round
	x = h + f1(e, f, g) + 0x748f82ee + words[56];
	y = f2(a, b, c);
	d += x;
	h = x + y;
	x = g + f1(d, e, f) + 0x78a5636f + words[57];
	y = f2(h, a, b);
	c += x;
	g = x + y;
	x = f + f1(c, d, e) + 0x84c87814 + words[58];
	y = f2(g, h, a);
	b += x;
	f = x + y;
	x = e + f1(b, c, d) + 0x8cc70208 + words[59];
	y = f2(f, g, h);
	a += x;
	e = x + y;
	x = d + f1(a, b, c) + 0x90befffa + words[60];
	y = f2(e, f, g);
	h += x;
	d = x + y;
	x = c + f1(h, a, b) + 0xa4506ceb + words[61];
	y = f2(d, e, f);
	g += x;
	c = x + y;
	x = b + f1(g, h, a) + 0xbef9a3f7 + words[62];
	y = f2(c, d, e);
	f += x;
	b = x + y;
	x = a + f1(f, g, h) + 0xc67178f2 + words[63];
	y = f2(b, c, d);
	e += x;
	a = x + y;

	// update hash
	m_hash[0] += a;
	m_hash[1] += b;
	m_hash[2] += c;
	m_hash[3] += d;
	m_hash[4] += e;
	m_hash[5] += f;
	m_hash[6] += g;
	m_hash[7] += h;
}

/// add arbitrary number of bytes
void SHA256::add(const void *data, size_t numBytes)
{
	const uint8_t *current = (const uint8_t *)data;

	if (m_bufferSize > 0) {
		while (numBytes > 0 && m_bufferSize < BlockSize) {
			m_buffer[m_bufferSize++] = *current++;
			numBytes--;
		}
	}

	// full buffer
	if (m_bufferSize == BlockSize) {
		processBlock(m_buffer);
		m_numBytes += BlockSize;
		m_bufferSize = 0;
	}

	// no more data ?
	if (numBytes == 0)
		return;

	// process full blocks
	while (numBytes >= BlockSize) {
		processBlock(current);
		current += BlockSize;
		m_numBytes += BlockSize;
		numBytes -= BlockSize;
	}

	// keep remaining bytes in buffer
	while (numBytes > 0) {
		m_buffer[m_bufferSize++] = *current++;
		numBytes--;
	}
}

/// process final block, less than 64 bytes
void SHA256::processBuffer()
{
	// the input bytes are considered as bits strings, where the first bit is the most significant bit of the byte

	// - append "1" bit to message
	// - append "0" bits until message length in bit mod 512 is 448
	// - append length as 64 bit integer

	// number of bits
	size_t paddedLength = m_bufferSize * 8;

	// plus one bit set to 1 (always appended)
	paddedLength++;

	// number of bits must be (numBits % 512) = 448
	size_t lower11Bits = paddedLength & 511;
	if (lower11Bits <= 448)
		paddedLength += 448 - lower11Bits;
	else
		paddedLength += 512 + 448 - lower11Bits;
	// convert from bits to bytes
	paddedLength /= 8;

	// only needed if additional data flows over into a second block
	unsigned char extra[BlockSize];

	// append a "1" bit, 128 => binary 10000000
	if (m_bufferSize < BlockSize)
		m_buffer[m_bufferSize] = 128;
	else
		extra[0] = 128;

	size_t i;
	for (i = m_bufferSize + 1; i < BlockSize; i++)
		m_buffer[i] = 0;
	for (; i < paddedLength; i++)
		extra[i - BlockSize] = 0;

	// add message length in bits as 64 bit number
	uint64_t msgBits = 8 * (m_numBytes + m_bufferSize);
	// find right position
	unsigned char *addLength;
	if (paddedLength < BlockSize)
		addLength = m_buffer + paddedLength;
	else
		addLength = extra + paddedLength - BlockSize;

	// must be big endian
	*addLength++ = (unsigned char)((msgBits >> 56) & 0xFF);
	*addLength++ = (unsigned char)((msgBits >> 48) & 0xFF);
	*addLength++ = (unsigned char)((msgBits >> 40) & 0xFF);
	*addLength++ = (unsigned char)((msgBits >> 32) & 0xFF);
	*addLength++ = (unsigned char)((msgBits >> 24) & 0xFF);
	*addLength++ = (unsigned char)((msgBits >> 16) & 0xFF);
	*addLength++ = (unsigned char)((msgBits >> 8) & 0xFF);
	*addLength = (unsigned char)(msgBits & 0xFF);

	// process blocks
	processBlock(m_buffer);
	// flowed over into a second block ?
	if (paddedLength > BlockSize)
		processBlock(extra);
}

/// return latest hash as 64 hex characters
std::string SHA256::getHash()
{
	// compute hash (as raw bytes)
	unsigned char rawHash[HashBytes];
	getHash(rawHash);

	// convert to hex string
	std::string result;
	result.reserve(2 * HashBytes);
	for (int i = 0; i < HashBytes; i++) {
		static const char dec2hex[16 + 1] = "0123456789abcdef";
		result += dec2hex[(rawHash[i] >> 4) & 15];
		result += dec2hex[rawHash[i] & 15];
	}

	return result;
}

/// return latest hash as bytes
void SHA256::getHash(unsigned char buffer[SHA256::HashBytes])
{
	// save old hash if buffer is partially filled
	uint32_t oldHash[HashValues];
	for (int i = 0; i < HashValues; i++)
		oldHash[i] = m_hash[i];

	// process remaining bytes
	processBuffer();

	unsigned char *current = buffer;
	for (int i = 0; i < HashValues; i++) {
		*current++ = (unsigned char)((m_hash[i] >> 24) & 0xFF);
		*current++ = (unsigned char)((m_hash[i] >> 16) & 0xFF);
		*current++ = (unsigned char)((m_hash[i] >> 8) & 0xFF);
		*current++ = (unsigned char)(m_hash[i] & 0xFF);

		// restore old hash
		m_hash[i] = oldHash[i];
	}
}

/// compute SHA256 of a memory block
std::string SHA256::operator()(const void *data, size_t numBytes)
{
	reset();
	add(data, numBytes);
	return getHash();
}

/// compute SHA256 of a string, excluding final zero
std::string SHA256::operator()(const std::string &text)
{
	reset();
	add(text.c_str(), text.size());
	return getHash();
}
